MARSEILLE/PARIS, Dec 10 (Reuters) - The founder of a French breast implant company was sentenced to four years in prison on Tuesday for hiding the true nature of the sub-standard silicone used in implants sold to 300,000 women around the world.

Jean-Claude Mas, 74, founder and long-time chief executive of Poly Implant Prothese (PIP), was prosecuted after a worldwide panic in 2011 when France recommended that women with such implants should have them removed due to an abnormally high rupture rate.

Worries about the implants launched a flurry of international lawsuits and prompted calls for Europe to toughen controls on medical devices and fix its fractured oversight system.

Once the third-largest global supplier of breast implants, the company was shut in 2010 and its implants ordered off the market after inspectors pursuing a tip-off discovered vats of industrial-grade silicone outside the PIP factory in the southern town of La-Seyne-sur-Mer.

A Marseille criminal court also ordered Mas, who had been pursued for aggravated fraud, to pay a 75,000-euro ($103,000) fine. His lawyer, Yves Haddad, said he would appeal.

Four other executives, including the chief financial officer, were sentenced to between one-and-a-half and three years in prison, some of it suspended, and fined.

“It’s a strong signal. This decision is what victims were waiting for,” said one of their lawyers, Philippe Courtois.

The president of a PIP victims group, Alexandra Blachere, called it a “symbolic sentence” that challenged any prejudice that there was “a ditzy bimbo behind every pair of silicone breasts.”

The two-month trial in April and May was held in an exhibition centre to accommodate the 7,400 civil plaintiffs and 300 lawyers. Jeers from the crowd greeted Mas’ appearance in the makeshift courtroom.

For less serious felonies in France, the criminal court hands down a sentence without pronouncing a guilty or not guilty verdict, which is implicit.

HIDDEN EVIDENCE

Mas admitted using silicone created by trial and error that was never approved by regulators and which cost a seventh of the price of silicone approved for use in medical devices.

He has insisted the gel he had relied on since the founding of the company in 1991 was non-toxic and has said women who complain about their PIP implants are “fragile people, or people who are doing it for the money.”

A police investigation revealed a sophisticated fraud at PIP, which managed to conceal the implants’ ingredients from regulators, thereby allowing them to be sold on international markets.

Before annual audits to the PIP factory by private certification company TUV Rheinland, employees would clear away evidence of the cheaper gel it used to fill implants.

TUV sued PIP for fraud, but a French court ruled last month the German company had failed in its obligations of “vigilance and caution” and ordered it to pay 3,000 euros to each of the 1,600 plaintiffs, women wearing PIP implants who had sued.

Health experts insist that no link has been established between PIP implants and breast cancer.

Still, women around the world with PIP implants, whether in Venezuela, France or Britain, have rushed to their surgeons to have them removed, fearing health complications.

Since France recommended removal, some 14,729 women in France - nearly half of all French women with PIP implants - have chosen this option, according to French regulators.

Regulators say a quarter of PIP implants removed were found to be faulty, most having ruptured.

Only one case of anaplastic large cell lymphoma, a rare type of cancer originating in the lymphatic system, has been documented in France from a women wearing PIP implants.

National health agencies have given differing advice. While France and Venezuela offered to reimburse women who have their PIP implants removed, other countries, such as Britain, recommended that women merely have them checked.

Other legal cases related to PIP are still pending in France, including one related to the 2010 death of a woman wearing PIP implants. Another relates to tax fraud by Mas, his former girlfriend and Chief Executive Claude Couty. ($1 = 0.7289 euros) (Writing By Alexandria Sage; Editing by Mark John and Ruth Pitchford)